1. Related Aoolications
This application claims priority under 35 USC 119 from GB 9008482.3 filed Apr. 17, 1990.
2. Field of the Invention
The present invention relates to upshift brakes for mechanical change gear transmissions.
3. Descriotion of the Prior Art
Mechanical change gear transmissions (i.e. utilizing positive jaw clutches to engage and disengage desired gear ratios) of the automatic, semi-automatic and manual types which utilize upshift brakes, also called "inertia brakes" and "input shaft brakes", to quickly retard the rotational speed of gearing and clutch members associated with the transmission input shaft to provide quicker synchronization during an upshift (as compared to relying on engine rotational speed decay) are well known in the prior art.
Examples of such prior art transmissions may be seen by reference to U.S. Pat. Nos. 4,873,637; 4,852,006; 4,676,115; 4,648,290; 4,614,126; 4,361,060 and 3,478,851, the disclosures of all of which are hereby incorporated by reference.
In manual transmissions, the upshift brake is typically operator actuated by a control switch, often a normally open switch closed upon full overtravel or bottoming of the manual clutch pedal, which selectively causes a retarding force to be applied directly to the input shaft or to gearing or shafts constantly drivingly engaged to the input shaft. Typically, the input shaft or upshift brake will include a gear constantly meshed with a transmission gear driven by the input shaft and a selectively engaged friction brake pack is provided to frictionally ground the upshift brake gear to the transmission housing. Typically, the friction brake pack is engaged/released by means of a hydraulic or pneumatic piston/cylinder assembly.
While the prior art upshift brakes are generally well received and commercially successful, they are not totally satisfactory as the upshift brake housings were subject to axial and/or torque loading which, due to the cyclical loading, required excessively costly and/or weighty robust housing designs and/or could result in housing or brake assembly fatigue and/or failure.